Magnetic positioning for inductive coupling

ABSTRACT

A magnetic positioning system for use in inductive couplings. The magnetic positioning system having a magnet that provides sufficient magnetic force, but does not have enough electrical conductivity to overheat in the presence of the anticipated electromagnetic field. The magnet may be a bonded magnet or a shielded magnet. In another aspect a plurality of magnets are used to provide magnetic attraction forces and said magnetic repulsion forces that cooperate to align the inductive power supply and the remote device. In another aspect, a sensor allows differentiation between different positions of the remote device or inductive power supply. In another aspect, multiple magnets in the inductive power supply interact with multiple magnets in the remote device to position the remote device in different positions.

This application claims the benefit of U.S. Provisional Application No.61/030,586, filed Feb. 22, 2008.

BACKGROUND OF THE INVENTION

The present invention relates to inductive coupling and moreparticularly to systems and methods for positioning a device within aninductive field.

With the advent of improved and less expensive electronics, there is agrowing use of wireless power supply systems. Wireless power supplysystems eliminate the need for cords and therefore eliminate theunsightly mess and the need to repeatedly connect and disconnect remotedevices. Many conventional wireless power supply systems rely oninductive power transfer to convey electrical power without wires. Atypical inductive power transfer system includes an inductive powersupply that uses a primary coil to wirelessly convey energy in the formof a varying electromagnetic field and a remote device that uses asecondary coil to convert the energy in the electromagnetic field intoelectrical power. To provide an inductive power transfer system withimproved efficiency, it is typically desirable to provide properalignment between the primary coil and the secondary coil. Alignment isoften achieved using cradles or other similar structures. For example,the primary coil may be positioned around the outside of a cup shaped toclosely receive the portion of the remote device containing thesecondary coil. When the remote device is placed in the cup, the twocoils become properly aligned. Although helpful in providing alignment,this approach requires deliberate placement of the remote device withinthe cradle. It may also limit the inductive power supply to use inconnection with a single device specially configured to fit within thecup or cradle.

It is known to provide an inductive lighting system for underwater usein a pool with a magnet as set forth in U.S. Publication No.2002/0008973 A1 to Boys et al, which was published on Jan. 24, 2002. Thepatent describes that the system may include a magnet for temporarilylocating lamp units. Although this reference discloses the use of amagnet for locating a light in the context of an inductive coupling, thesparse disclosure relating to magnets fails to address a number ofissues. First, the reference does not disclose where the magnets arelocated and whether or not magnets are included in both the inductivepower supply and the lamp units. Second, the reference fails to show anyrecognition or offer any solution for the inherent tendency of typicalmagnets to heat in the presence of an electromagnetic field. Third, thepatent fails to recognize the need for or provide any solution toaddress orientation of the remote device with respect to the inductivepower supply.

SUMMARY OF THE INVENTION

The present invention provides a magnetic positioning system for use ininductive couplings. In one aspect, the present invention provides amagnetic positioning system having a magnet that provides sufficientmagnetic force, but does not have enough electrical conductivity tooverheat in the presence of the anticipated electromagnetic field. Inone embodiment, the magnet is a bonded magnet having particles of a rareearth magnet bound together by a binder. The bonded magnet may includeneodymium particles combined with an epoxy binder.

In a second aspect, the present invention provides a magneticpositioning system having a supplemental magnet to enhance the magneticforce of a principal magnet. In one embodiment, the supplemental magnetis positioned sufficiently close to the primary magnet to allow themagnetic field from the supplemental magnet to combine with andstrengthen the magnetic field of the primary magnet. The primary magnetmay be positioned within and subject to the full electromagnetic field,but be sufficiently non-conductive that it does not overheat. Thesupplemental magnet may be relatively conductive, but may be shielded sothat it is subject to a lesser magnetic field and therefore does notoverheat. The system may include a shield, such as a ferrite plate,positioned between the supplemental magnet and the primary magnet. Theshield may be sized and shaped to adequately reduce the amount of theelectromagnetic field reaching the supplemental magnet.

In a third aspect, the present invention provides a magnet positioningsystem having an arrangement of magnets configured to provide properorientation between the remote device and the inductive power supply.The power supply and remote device may include magnets arranged inmatching patterns to aid in optimal coil alignment.

These and other objects, advantages, and features of the invention willbe readily understood and appreciated by reference to the detaileddescription of the current embodiment and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an inductive power supply and remotedevice in accordance with an embodiment of the present invention.

FIG. 2 is a sectional view of the inductive power supply and remotedevice.

FIG. 3 is an illustration of a remote device incorporating a secondarymagnet.

FIG. 4 is an illustration of an inductive power supply and a remotedevice.

FIG. 5 is an exploded perspective view of portions of a firstalternative embodiment having a supplemental magnet and shield.

FIG. 6 is a sectional view of the first alternative embodiment.

FIG. 7 is a representational view of a primary magnet layout andcorresponding secondary magnet layout.

FIG. 8 is a representational view of an alternative magnet layout.

FIG. 9 is a representational view of a second alternative magnet layout.

FIG. 10 is a representational view of a third alternative magnet layout.

FIG. 11 is a representational view of primary and secondary magnets inaccordance with a fourth alternative magnet layout.

FIG. 12 is a representational view of an alternative embodiment having abar magnet.

FIG. 13 is a representational view of primary and secondary magnetlayouts of an alternative embodiment in which the magnetic positioningsystem may be used to determine the orientation of the remote device.

FIG. 14 is a cross sectional view showing an alternative embodiment ofthe present invention with a flush primary magnet and a shieldedsupplemental magnet.

FIG. 15 is a cross sectional view showing an alternative embodiment ofthe present invention with an extended primary magnet and a shieldedsupplemental magnet.

FIG. 16 is a cross sectional view showing an alternative embodiment ofthe present invention with a flush primary magnet seated in a shield.

FIG. 17 is a cross sectional view showing an alternative embodiment ofthe present invention with an extended primary magnet seated in ashield.

FIG. 18 is a cross sectional view showing an alternative embodiment ofthe present invention with a primary magnet recessed into a shield.

FIG. 19 is a cross sectional view showing an alternative embodiment ofthe present invention with a primary magnet partially recessed into ashield.

FIG. 20 is a cross sectional view showing an alternative embodiment ofthe present invention with a flush primary magnet disposed within asleeve in a shield.

FIG. 21 is a cross sectional view showing an alternative embodiment ofthe present invention with an extended primary magnet disposed within asleeve in a shield.

FIG. 22 is a cross sectional view showing an alternative embodiment ofthe present invention with a primary magnet disposed within a recessedsleeve in a shield.

FIG. 23 is a cross sectional view showing an alternative embodiment ofthe present invention with a primary magnet disposed within a partiallyrecessed sleeve in a shield.

FIG. 24 is a cross sectional view showing an alternative embodiment ofthe present invention with a primary magnet partially disposed within asleeve in a shield.

FIG. 25 is a cross sectional view similar to FIG. 24 showing theunshielded portion of the primary magnet extending through a chargingsurface.

FIG. 26 is a cross sectional view showing an alternative embodiment ofthe present invention with a flush primary magnet disposed within acavity in a shield.

FIG. 27 is a cross sectional view showing an alternative embodiment ofthe present invention with an extended primary magnet disposed within acavity in a shield.

FIG. 28 is a cross sectional view showing an alternative embodiment ofthe present invention with a flush primary magnet disposed within arecessed cavity in a shield.

FIG. 29 is a cross sectional view showing an alternative embodiment ofthe present invention with an extended primary magnet disposed within apartially recessed cavity in a shield.

FIG. 30 is a cross sectional view showing an alternative embodiment ofthe present invention with a flush primary magnet disposed within aninverted cavity in a shield.

FIG. 31 is a cross sectional view showing an alternative embodiment ofthe present invention with an extended primary magnet disposed within aninverted cavity in a shield.

FIG. 32 is a cross sectional view showing an alternative embodiment ofthe present invention with a primary magnet disposed within an inverted,recessed cavity in a shield.

FIG. 33 is a cross sectional view showing an alternative embodiment ofthe present invention with a primary magnet disposed within an inverted,partially recessed cavity in a shield.

DESCRIPTION OF THE CURRENT EMBODIMENT

An inductive power supply and remote device incorporating a magneticpositioning system in accordance with the present invention are shown inFIG. 1. The inductive power supply 10 generally includes power supplycircuitry 12 and a primary coil 14. The remote device 16 generallyincludes a secondary coil 18 and a load 20. The magnetic positioningsystem 22 generally includes a primary magnet 24 positioned in theapproximate center of the primary coil 14 and a secondary magnet 26positioned in the approximate center of the secondary coil 18. The twomagnets 24 and 26 are oriented to attract one another and thereforeassist in providing proper alignment between the power supply 10 and theremote device 16. The magnets 24 and 26 are sufficientlynon-electrically conductive that they do not heat beyond acceptablelimits in the presence of the electromagnetic field.

The present invention is suitable for use with essentially any inductivepower supply. Accordingly, the inductive power supply 10 will not bedescribed in detail. Suffice it to say that the inductive power supply10 includes power supply circuit 12 and a primary coil 14. The powersupply circuit 12 generates and applies alternating current to theprimary coil 14. As a result of the alternating current applied by thepower supply circuit 12, the primary coil 14 generates anelectromagnetic field. The power supply circuit 12 may be essentiallyany circuitry capable of supplying alternating current to the primarycoil 14 at the desired frequency or frequencies. For example, the powersupply circuit 12 may be the resonant seeking circuit of the inductivepower supply system disclosed in U.S. Pat. No. 6,825,620, which isentitled “Inductively Coupled Ballast Circuit” and issued Nov. 30, 2004,to Kuennen et al; the adaptive inductive power supply of U.S. Pat. No.7,212,414, which is entitled “Adaptive Inductive Power Supply” andissued May 1, 2007, to Baarman; or U.S. Pat. No. 7,522,878, which isentitled “Adaptive Inductive Power Supply with Communication” and issuedApr. 21, 2009, to Baarman (identified above)—all of which areincorporated herein by reference in their entirety.

The primary coil 14 of the illustrated embodiment is a circular coil ofwire suitable for generating an electromagnetic field. In someapplications, the primary coil 14 may be a coil of Litz wire. Thecharacteristics of the coil may vary from application to application.For example, the number of turns, size, shape and configuration of thecoil may vary. Further, the characteristics of the wire may vary, suchas length, gauge and type of wire. Although described in connection witha coil of wire, the primary coil 14 may alternatively be essentially anystructure capable of generating a suitable electromagnetic field. In oneembodiment, the primary coil 24 (or secondary coil 26) may be replacedby a printed circuit board coil, such as a printed circuit board coilincorporating the inventive principles of U.S. Ser. No. 60/975,953,which is entitled “Printed Circuit Board Coil” and filed on Sep. 28,2007 by Baarman et al, and a priority document of U.S. Pat. No.7,973,635 filed on Sep. 24, 2008 and issued Jul. 5, 2011. The content ofU.S. Ser. No. 60/975,953 is incorporated herein by reference in itsentirety.

The magnetic positioning system 22 includes a primary magnet 24incorporated into the inductive power supply 10. Although the positionof the primary magnet 24 may vary, the primary magnet 24 may be disposedwithin the primary coil 14. For example, in applications that include agenerally circular primary coil 14, the primary magnet 24 may becoaxially positioned within the primary. The primary magnet 24 ismanufactured from a material that is capable of providing sufficientmagnetic force, but at the same time is not sufficiently electricallyconductive to heat excessively in the presence of the electromagneticfield generated by the primary coil 14. The amount of heat acceptable ina given situation will vary depending on the application, for example,depending on the ability of the surrounding materials and closelypositioned electronics to withstand heat. In one embodiment, the primarymagnet is a bonded magnet, such as a compression molded or injectionmolded magnet. For example, bonded rare earth magnets have provensuitable, including bonded neodymium and samarium cobalt magnets. Thebinder may vary from application to application, but in the illustratedembodiment is a non-electrically conductive epoxy. In some applications,it may be possible to form a suitable bonded magnet without a binder.Although rare earth bonded magnets have proven to be suitable, a varietyof alternative magnets may also be suitable depending on theelectromagnetic field, the required magnetic force and the tolerance forheat build-up. For example, the primary magnet 24 may be a ceramicferrite magnet. Typical ceramic ferrite magnets may have a magnetic fluxdensity that is substantially less than typical rare earth bondedmagnets. Accordingly, they may be more suitable in applications whereless magnetic force is required.

In addition to assisting in initial placement of the remote device, themagnetic positioning system may be used to maintain the remote device inthe proper position over time. In applications where it is desirable toretain the remote device is a specific orientation while it is on theinductive power supply, the magnetic positioning system may incorporatemultiple magnets, as described in more detail below. To provide thesefunctions, the magnets may be sized with sufficient flux density to holdthe device in place despite potential external forces, such as gravityand vibration. For example, the magnets may have sufficient strength tohold the remote device on an incline or slanted surface, which mayprovide an improved viewing angle or facilitate use of the remote devicewhile it is on the inductive power supply. In some applications, themagnets may have sufficient flux density to hold the remote device inplace despite acceleration and deceleration forces, such as whencharging the remote device in a moving vehicle. In those applicationswhere a user may interact with the remote device while it is on theinductive power supply, the magnets may have sufficient strength to holdthe device in place despite user interaction. For example, a user maypush a button or manipulate a touch screen to operate a phone or adigital media player. In some applications, manipulation of the deviceas a whole may be desirable. For example, there may be applicationswhere spinning a remote device while it is on the inductive power supplyis used for special effects or user input (e.g. a gaming controller,control adjustment and display realignment). In such applications, themagnet strength and configuration may be set to hold the device inposition while it is spun or rotated.

The inductive power supply 10 may be contained within a housing 30, suchas a dedicated housing having a surface 32 on which to place the remotedevice 16. The size, shape and configuration of the surface 32 may vary.For example, the surface 32 may be flat (as shown) or it may becontoured to receive one or more remote devices 16. The surface 32 mayinclude a low friction material to enhance the ability of the magnets 24and 26 to draw the remote device 16 into proper alignment.Alternatively, the inductive power supply 10 may be housed within a worksurface, such as a desktop, table top or counter top. In theseembodiments, the remote device 16 may be placed directly of the worksurface in which the inductive power supply is contained. As anotheralternative, the inductive power supply 10 may be disposed within aceiling or within a wall or other inclined/vertical surface. Forexample, the inductive power supply 10 may be used to supply power to aceiling-mount or wall-mount light fixture (not shown). In ceiling-mountand wall-mount applications, the magnetic positioning system may be usedto secure the remote device (e.g. the light fixture) to the ceiling orwall, thereby eliminating the need for other mechanical fasteners. Thiswill not only facilitate installation, but will also simplifyreplacement of light fixtures or other remote devices. The strength ofthe magnetic positioning system 22 may vary from application toapplication. In some applications, it may be desirable to havesufficient force to draw the remote device 16 into proper alignment fromwithin a specific range (e.g. 3 centimeters). The amount of magneticforce required to center the remote device from a given range willdepend in large part on the contour/shape and coefficient of friction ofthe inductive power supply surface 32, as well as on the weight andcoefficient of friction of the remote device 16. In other applications,it may be desirable to have sufficient magnetic strength to support aremote device on a ceiling or a wall. In such applications, the weightof the remote device 16 will play a key role in determining theappropriate magnetic strength. In still other application, it may bedesirable simply to provide a noticeable magnetic draw toward properalignment. In such applications, it may be necessary to manually movethe remote device 16 into proper alignment, but the magnetic force mayprovide a perceptible guide.

As noted above, the remote device 16 generally includes a secondary coil18 and a load 20. The remote device 16 is illustrated representativelyin the drawings, but it may be essentially any device or component thatoperates on or otherwise responds to an electromagnetic field. Forexample, the remote device 16 may be an active device having a load 20that operates on electrical power received inductively from theinductive power supply 10, such as a cell phone, personal digitalassistant, digital media player or other electronic device that may useinductive power to recharge an internal battery. As another example, theremote device 16 may be a passive device that achieves a functionthrough the direct application of an electromagnetic field to the load20, such as an inductive heater that is directed heated by theelectromagnetic field. In typical passive applications, the remotedevice 16 will not include a secondary coil 18. However, the magneticpositioning system 22 may still be used to provide proper alignmentbetween the primary coil 14 and the element (e.g. the load) of theremote device 16 that is intended to receive the electromagnetic field.

The secondary coil 18 of the illustrated embodiment is a circular coilof wire suitable for generating electricity when in the presence of avarying electromagnetic field. As shown, the secondary coil 18 maycorrespond in size and shape to the primary coil 14. For example, thetwo coils 14 and 18 may have substantially equal diameters. In someapplications, the secondary coil 18 may be a coil of Litz wire. As withthe primary coil 14, the characteristics of the secondary coil 18 mayvary from application to application. For example, the number of turns,size, shape and configuration of the secondary coil 18 may vary.Further, the characteristics of the wire may vary, such as length, gaugeand type of wire. Although described in connection with a coil of wire,the secondary coil 18 may alternatively be essentially any structurecapable of generating sufficient electrical power in response to theintended electromagnetic field.

The magnetic positioning system 22 includes a secondary magnet 26 thatis incorporated into the remote device 16. The secondary magnet 26 ispositioned to correspond with the primary magnet 24. More specifically,the secondary magnet 26 is positioned at a location where it willprovide proper alignment between the secondary coil 18 and the primarycoil 14 when the primary magnet 24 and the secondary magnet 26 arealigned. In the illustrated embodiment, the secondary magnet 26 isdisposed substantially coaxially within the secondary coil 18. In thisposition, the magnetic positioning system 22 aligns the primary coil 14and the secondary coil 18 regardless of the orientation of the remotedevice 16 about the axis of the secondary coil 18. As with the primarymagnet 24, the secondary magnet 26 is manufactured from a materialcapable of providing sufficient magnetic force, but at the same time notsufficiently electrically conductive to heat excessively in the presenceof the electromagnetic field generated by the primary coil 14. Theamount of heat acceptable in the remote device 16 will vary depending,for example, on the ability of the surrounding materials and closelypositioned electronics to withstand heat. The secondary magnet 26 may bea bonded magnet, such as a compression molded or injection moldedmagnet. The secondary magnet 26 may be a bonded rare earth magnet,including a bonded neodymium magnet or a bonded samarium cobalt magnet.As with the primary magnet 24, the binder is a non-electricallyconductive epoxy, but may vary from application to application and maybe eliminated in some application. The secondary magnet 18 may be any ofa variety of alternative magnets capable of providing suitable magneticforce without excessive heat build-up. For example, the secondary magnet26 may be a ceramic ferrite magnet.

Although the primary magnet 24 and the secondary magnet 26 are bothmanufactured from materials that have limited RF absorption andtherefore limited heating, in some applications it may not be necessaryfor both magnets to have these characteristics. For example, in someapplications, it may be possible for either the primary magnet 24 or thesecondary magnet 26 to be a typical sintered rare earth magnet. This ismost likely to be possible in application where either the inductivepower supply or the remote device has a high tolerance to temperature orwhere the electromagnetic field is sufficiently weak that one of the twomagnets does not undergo excessive heating.

Experience has revealed that magnet size is also relevant to heatbuild-up. For example, it may be possible to reduce heating by reducingmagnet volume. In the context of a cylindrical magnet, heating may bereduced by decreasing diameter and/or height of the magnet.

In alternative embodiment, the magnets 24 and 26 may be used to move theprimary coil 12 rather than the remote device (not shown). To achievethis objection, the primary coil 14 may be loosely positioned within theinductive power supply 10. For example, the primary coil 14 may befreely placed within a void of substantially greater size in the desireddirection of motion. When the remote device 16 is placed withinsufficient distance of the primary coil 14, the magnetic positioningsystem 22 will move the primary magnet 24 and consequently the primarycoil 14 to an aligned position beneath the secondary magnet 26 in theremote device 16.

FIGS. 3 and 4 are photographs showing a specific implementation of anembodiment of the present invention. FIG. 3 is a photograph of acellular telephone 716 with the battery cover (not shown) removed toshow the secondary coil 718 and secondary magnet 726. As can be seen,the secondary coil 718 and secondary magnet 726 are coaxially disposedwithin the battery compartment of the cellular telephone 716. Thecellular telephone 716 may include a special battery compartment door(not shown) to accommodate the secondary coil 718 and secondary magnet726. For example, the battery compartment may be closed with an enlargedbattery cover (not shown), such as the type used to accommodate anextended life battery. FIG. 4 is a photograph showing the cellulartelephone 716 resting atop an inductive power supply 710. The inductivepower supply 710 includes a transparent cover that defines the chargingsurface 732. The cellular telephone 716 is not shown in proper alignmentwith the inductive power supply 710 to permit viewing of the primarycoil 714 and primary magnet 724 through the transparent cover. As can beseen, when the cellular telephone 716 is positioned with secondarymagnet 726 in alignment with primary magnet 724, the secondary coil 718will be aligned with the primary coil 714, thereby facilitatingefficient operation of the system.

An alternative embodiment of the present invention is shown in FIGS. 5and 6. In this embodiment, at least one of the magnets 24 and 26 isenhanced by a supplemental magnet. For purposes of disclosure, thisaspect of the invention will be described in connection with the use ofa supplemental magnet 60 in the inductive power supply 10′. Except asdescribed, the inductive power supply 10,′ remote device 16′ andmagnetic positioning system 22′ are essentially identical to thosedescribed above. Referring now to FIG. 6, the inductive power supply 10′generally includes an inductive power circuit 12′ and a primary coil14′, and the remote device 16′ generally includes a secondary coil 18′and a load 20′. The magnet positioning system 22′ generally includes aprimary magnet 24′, a supplemental magnet 60, a shield 62 and asecondary magnet. The primary magnet 24′, supplemental magnet 60 andshield 62 are positioned in the inductive power supply 10′. As shown,the primary magnet 24′ may be coaxially positioned within the primarycoil 14′. The shield 62 may be positioned below the primary coil 14′ andthe primary magnet 24′. The supplemental magnet 60 of this embodiment ispositioned immediately below the shield 62 opposite the primary magnet24′. The supplemental magnet 60 may be coaxially aligned with theprimary magnet 24′. The shield 62 is configured to reduce the amount ofthe electromagnetic field that reaches the supplemental magnet 60. Toachieve this end, the illustrated shield 62 is large enough to be atleast coextensive with the primary coil 14′. The size, shape andconfiguration of the shield 62 may, however, vary from application toapplication depending in part on the size, shape and configuration ofthe primary coil 14′ and the supplemental magnet 60, as well as on thedesired amount of heat protection. The supplemental magnet 60 may beessentially any magnet capable of supplementing the magnetic field ofthe primary magnet 24′ to produce suitable magnetic force. For example,the supplemental magnet 60 may be a rare earth magnet, such as asintered rare earth magnet. In use, the magnetic field from thesupplemental magnet 60 will combine with the magnetic field from theprimary magnet 24′. The combined magnetic fields will provide greatermagnetic force than the primary magnet 24′ would have provided on itsown. The shield 62 provides sufficient isolation of the supplementalmagnet 60 from the electromagnetic field of the primary coil 14′ toprevent excessive heating. For example, the shield 62 will act as anelectromagnetic field guide that causes a portion of the electromagneticfield that would have otherwise encompassed the supplemental magnet 62to pass through the shield 62 above the supplemental magnet 62. As aresult, the supplemental magnet 60 helps to improve magnetic forcewithout creating the degree of heat generation that would have occurredif the supplemental magnet 60 had been placed directly in theelectromagnetic field.

The present invention also provides a magnetic positioning systemcapable of assisting placement of a remote device in the appropriateorientation using a plurality of magnets. A variety of alternativeembodiments illustrating this aspect of the invention are shown in FIGS.7-12. For purposes of disclosure, this aspect of the invention will bedescribed with reference to representation views of various exemplarymagnet layouts. These and other magnet layouts may be incorporated intoessentially any inductive power supply system. The magnet pattern isselected to provide full magnetic alignment of the remote device at thedesired orientation(s). In multiple magnet embodiments, it may bepossible for one or more of the individual magnets to be a sintered rareearth magnet (or other type of electrically conductive magnet) providedthat that particular magnet is located sufficiently remote from theelectromagnetic field that it does not generate excessive heat. FIG. 7shows a primary magnet 124 having a pair of magnets 124 a-b and asecondary magnet 126 having a pair of magnets 126 a-b located incorresponding positions. With this layout, the magnetic positioningsystem 122 will provide the greatest attractive force when the magnets124 a-b and 126 a-b are aligned. When the remote device is positioned sothat the corresponding magnets are aligned, the primary coil 114 and thesecondary coil 118 will be properly aligned to facilitate efficientoperation. In some applications, the magnetic positioning system 122 maybe able to draw the remote device (not shown) into optimal alignment. Inother applications, the user may need to adjust the remote device untilproper alignment can be felt through magnetic attraction. Referring nowto FIG. 8, the primary magnet 224 may include a plurality of separatemagnets 224 a-f that are arrange in a specific pattern. Although notshown, the secondary magnet 226 may also include a plurality of separatemagnets 226 a-f. The magnets 226 a-f making up the secondary magnet 226may be arranged in an identical and complimentary pattern with respectto the individual magnets 224 a-f of the primary magnet 224.Alternatively, the secondary magnet 226 may include a different numberand arrangement of magnets, provided that they are configured to provideproper orientation when positioned adjacent to the primary magnet 224.The magnet layout of magnetic positioning system 222 provides threeorientations at which full magnetic attraction occurs. The layout ofmagnetic positioning system 222 may help a user avoid placing the remotedevice 216 in an incorrect position because a properly aligned remotedevice will result in magnetic force from all six aligned magnets, whilethe maximum misaligned force with come from two magnets. The differencein attractive force between these two positions should be apparent to auser. Another alternative layout is shown in FIG. 9. In this embodiment,the magnetic positioning system 322 includes a primary magnet 324 with aplurality of separate magnets 324 a-f that are arranged in a somewhatdifferent pattern that magnets 224 a-f. Although not shown, thesecondary magnet may also include a plurality of separate magnetsarranged in an identical and complimentary pattern with respect to theindividual magnets 324 a-f of the primary magnet 324. Alternatively, thesecondary magnet may include a different number and arrangement ofmagnets, provided that they are configured to provide proper orientationwhen positioned adjacent to the primary magnet 324. The magnet layout ofmagnetic positioning system 322 provides three orientations at whichfull magnetic attraction occurs. As with the layout of FIG. 8, thislayout may help a user avoid placing the remote device in an incorrectposition.

In some embodiments, this tactile feedback provided by the magneticpositioning system is sufficient to allow the user to align the magnetswithin a magnetic hot spot on a blind surface. That is, no markings orother indications are necessary to allow the user to align the magnets.As the user adjusts the remote device, the amount of magnetic attractionand magnetic repulsion may change based on the location of the remotedevice. By moving the remote device towards any magnetic attraction andaway from any magnetic repulsion, the user can guide the remote deviceto one or more suitable alignment locations. This adjustment can be made“blind” without the user looking at the surface. In one embodiment, theuser could align the remote device for charging while performing anactivity that demands visual attention, such as for example driving.

Although the embodiments of FIGS. 7-9 show the plurality of magnets 124a-f within the primary coil 114, the primary magnet 124 may be arrangedwith some or all of the individual magnets 124 a-f outside the primarycoil 114. For example, FIG. 10 shows a primary magnet 424 with fourmagnets 424 a-d positioned outside the primary coil 414. Again, thesecondary magnet (not shown) may include a matching arrangement of fourmagnets or it may include some other number of magnets provided thatthey are arranged to give maximum magnetic attraction when the remotedevice is positioned in the proper orientation(s).

The embodiment of FIG. 11 show an example of a magnetic positioningsystem in which the magnet layout in the primary magnet 624 is differentfrom the magnet layout in the secondary magnet 626. The primary magnet624 is positioned within the primary coil 614 and the secondary magnet626 is positioned within the secondary coil 618. As can be seen, theprimary magnet 624 includes a plurality of magnets 624 a-g arranged withsix magnets of one polarity forming a ring about a seventh magnet ofopposite polarity. The secondary magnet 626 includes a single magnetmatching the polarity of the central magnet 624 g of the primary magnet624. The plurality of magnets 624 a-f and secondary magnet 626 provide amagnetic repulsion force. The magnet 624 g and the secondary magnet 626provide a magnetic attraction force. The magnetic attraction force andsaid magnetic repulsion force cooperate to align the inductive powersupply and the remote device.

Although the magnets are shown as cylindrical magnets, the shape of themagnets may vary from application to application as desired. A barmagnet may be used in application where it is desirable for a remotedevice to be positioning essentially anywhere along the length of thebar magnet. For example, in connection with a track lighting assembly,the primary magnet 524 may be a bar magnet located within a primary coil514. The primary coil 514 may be an oval or otherwise elongated coil.The bar magnet 524 may permit one or more remote devices 516 (e.g. lightfixtures) to be placed at different positions along the extent of theprimary coil 514. The remote device 516 may include a single magnet 526when it is not necessary or desirable for the magnetic positioningsystem 522 to assist in positioning the remote device 516 in a specificorientation. Alternatively, the remote device 516′ may include multiplemagnets 526 a-b′ when assistance in establishing a specific orientationis desired.

The magnetic positioning system may also be used to determine theorientation of the remote device with respect to the inductive powersupply. This information may be used to provide input to the remotedevice, such as control information. The remote device may act on theinput or it may pass the input on to another device. As an example ofthe former, the magnetic positioning system may be used to determinewhether to operate the display on the remote device in portrait orlandscape mode. As an example of the latter, the remote device mayitself be a control for another device. In this example, a user maychange the orientation of the remote device to provide an input to theother device. The magnetic positioning system may also be capable ofdetermining direction of rotation, for example, clockwise or counterclockwise rotation of the remote device. Information about the directionof rotation may, among other things, be useful in implementing commandsin the remote device or another device. For example, direction ofrotation may be used as a volume control input with clockwise rotationbeing an input signal to increase volume or brightness andcounterclockwise rotation being an input signal to decrease volume orbrightness. FIG. 13 is a representation of the primary magnet layout andthe secondary magnet layout for one embodiment of this aspect of theinvention. In this embodiment, the remote device is capable of beingpositioned in one of eight unique orientations. As shown, the primarymagnet 824 includes nine individual magnets 824 a-i arranged within theprimary coil 814, and the secondary magnet 826 includes two individualmagnets 826 a-b located within the secondary coil 818. To align theremote device, the central primary magnet 824 a and the centralsecondary magnet 826 a are aligned and the outer secondary magnet 826 bis aligned with any one of the eight outer primary magnets 824 b-i,thereby giving eight unique orientations. The primary magnet 824 mayalso include an indexing magnet 824 j that functions as a referencemagnet to create differentiation in the magnetic field between differentorientations of the remote device 816. In this embodiment, the indexingmagnet 824 j is located outside the primary coil 814, but that is notstrictly necessary. For example, one or more indexing magnets may belocated at other positions in or around the inductive power supply or atlocations other than in the inductive power supply, such as in anadjacent structure. The remote device 816 may also include one or moreHall effect sensors 850 (or other components capable of measuring amagnetic field) that provide information regarding the magnet fieldsurrounding the remote device 816. Multiple sensors may improve theability of the system to accurately assess the orientation or motion ofthe remote device. The position of the Hall effect sensor may vary fromapplication to application. For example, two Hall effect sensorsarranged at different locations and in different orientations mayprovide improved sensitivity or accuracy. Given the presence of theindexing magnet 824 j, the readings of the Hall effect sensor(s) 850will uniquely vary from one orientation of the remote device 816 toanother. A controller (not shown) within the remote device 816 maycompare the readings obtained from the Hall effect sensor(s) with alook-up table to determine the orientation of the remote device 816and/or the control, function or other action associated with thespecific orientation. In this way, the orientation of the remote device816 may be used to provide an input or control signal to the remotedevice 816. The remote device 816 may act on that input or controlsignal internally or it may be sent to another device. Although theillustrated embodiment includes an indexing magnet 824 j, an indexingmagnet may not be necessary in all applications. For example, in thoseapplications where the sensor will receive unique readings throughoutthe range of possible orientations without an indexing magnet, anindexing magnet may not be necessary. Examples of applications in whichan indexing magnet may not be necessary include situations where themagnet layout of the primary is not uniform or symmetric. Anotherexample of an application where an indexing magnet may not be requiredis an application where the electromagnetic field generated by theprimary gives the sensor readings sufficient differentiation fromorientation to orientation. Although described in connection withdetermining orientation/motion on the remote device side of theinductive coupling, orientation/motion may alternatively or additionallybe determined on the inductive power supply side of the inductivecoupling. For example, the orientation or motion of the remote devicemay be used as a control signal for the inductive power supply or someother device in communication with the inductive power supply. Inapplications where the sensor(s) (e.g. Hall effect sensor) is located onthe inductive power supply side of the inductive coupling, it may benecessary to add an indexing magnet to the remote device to create thedesired degree of differentiation in the sensor readings from oneorientation of the remote device to another.

The magnetic positioning system may continue to supply power duringmovement of the remote device. That is, the inductive power supply maysupply power while the remote device is in a first position, throughoutmovement of the remote device, and while the remote device is in asecond position. For example, the remote device may be rotatable 360degrees through the use of the magnetic positioning system. Theinductive power supply may supply power while the remote device is atrest in a first orientation, while the remote device is being rotated,and while the remote device is at rest in a second orientation. Inanother example, the inductive power supply may supply power while theremote device is in a first resting position on a power transfersurface, while the remote device is slid around the power transfersurface, and while the remote device is in a second resting position onthe power transfer surface. In some embodiments, the remote device maycontinue to be supplied power while being separated from the powertransfer surface. Once the remote device is brought out of proximity ofthe inductive power supply, power transfer stops. When the remote deviceis brought back within proximity of the inductive power supply, powertransfer may resume or restart. If necessary, the inductive power supplymay make adjustments to maintain the power transfer accounting fordifferences in the positional relationship. For example, in someembodiments, the inductive power supply may make an adjustment or acombination of adjustments to the operating frequency, resonantfrequency, rail voltage, or a number of other inductive power supplyparameters.

Various embodiments of shielding a magnet from some or all of theelectromagnetic field generated during transfer of power from aninductive power supply to a remote device are illustrated in FIGS.14-33. These embodiments are described in the context of an inductivepower supply, but are applicable where the magnet and shield arecontained within the remote device. Although there may be variations inthe components from embodiment to embodiment, to ease the description,similar reference numerals have been used to describe similarcomponents. The magnets in the embodiments described provide a magneticforce for alignment of the inductive power supply and the remote device.The shield in these embodiments is configured to reduce theelectromagnetic field that reaches the magnet during wireless powertransfer from the inductive power supply to the remote device.

Referring to FIGS. 14 and 15, alternative embodiments of the shieldedsupplemental magnet illustrated in FIGS. 5 and 6 are shown. In FIGS. 5and 6, the supplemental magnet 60 is somewhat larger than the primarymagnet 24. FIG. 14 illustrates that the supplemental magnet 960 andprimary magnet 924 may be equal in size. Further, the FIG. 14 embodimentillustrates that the primary magnet may be flush with the surface of thecoil 914. FIG. 15 illustrates that the primary magnet 924 may be largerthan the supplemental magnet 960. Further, the FIG. 15 embodimentillustrates that the primary magnet may extend above the height of thecoil 915. Although not depicted explicitly in this specific embodiment,the size, shape and height of the magnet may vary. The coil 914 and theshield 962 in these embodiments are positioned similarly and operatesimilarly as described above in connection with the FIGS. 5 and 6embodiment.

Referring to FIGS. 16-19, the depicted alternative embodiments includesa single magnet 924 disposed within a hole 925 of a shield 962. Themagnet 924 may be flush with the shield and the surface of the coil 914,as shown in FIG. 16. The magnet 924 may be flush with the shield 962 andextend above the height of the coil 914, as shown in FIG. 17. One sideof the magnet 924 may be flush with the shield 962 and the other siderecessed into the shield as shown in FIG. 18. The magnet 924 may bepartially recessed into the shield 962 as shown in FIG. 19. Theseillustrated embodiments of a magnet disposed within a shield are merelyexemplary.

Referring to FIGS. 20-24, the depicted alternative embodiments include asingle magnet 924 disposed within a sleeve 927 of a shield 962. Thesleeve may be integrally formed with the shield or connected with theshield. The sleeve may be made of the same or a different material fromthe shield 962. Both sides of the magnet 924 may be flush with thesleeve 927 as shown in FIGS. 20-24. The magnet, sleeve, and surface ofthe coil 914 may all be flush as shown in FIG. 20.

FIG. 21 is a cross sectional view showing an alternative embodiment ofthe present invention with an extended primary magnet 924 disposedwithin a sleeve 927 in a shield. The magnet 924 and sleeve 927 may bothextend above the surface of the coil 914, as shown in FIG. 21. FIG. 21includes a charging surface 929 where the sleeve 927 and the magnet 924jut through the charging surface. This configuration allows the magnet924 and shield or core 927 to protrude through a surface for additionaltactile feedback. For example, smaller magnets may provide betterelectromagnetic coupling with this configuration. In alternativeembodiments, the charging surface may be flush with one or both of thesleeve and magnet or the sleeve and magnet may be below the chargingsurface.

Referring to FIG. 22, one side of the magnet 924 and sleeve 927 may beflush with the shield 962 and the other side of the magnet 924 and thesleeve 927 may be recessed into the shield 927. The magnet 924 andsleeve 927 may be partially recessed into the shield 962 as shown inFIG. 23. Alternatively, one or both sides of the magnet may extend aboveor below the sleeve.

FIG. 24 is a cross sectional view showing an alternative embodiment ofthe present invention with a primary magnet 924 partially disposedwithin a sleeve 927 in a shield. That is, one side of the magnet 924 maybe flush with the sleeve 927 and the other side of the magnet 924 mayextend above the sleeve 927 as shown in FIG. 24. FIG. 24 includes acharging surface 929 with a hole where the magnet 924 juts through thehole in the charging surface 929. This configuration allows the magnet924 to protrude through a surface for additional tactile feedback. Forexample, smaller magnets may provide electromagnetic coupling with thisconfiguration.

Referring to FIGS. 25-33, the depicted alternative embodiments include asingle magnet 924 disposed within a cavity 930 of a shield 962. Thecavity may be integrally formed with the shield or a separate piececonnected to the shield 962. The cavity may be made of the same or adifferent material from the shield 962. One side of the magnet 924 maybe seated within the cavity 930 and the other side of the magnet 924 mayextend above the cavity 930 such that the side is flush with a chargingsurface 929, as shown in FIG. 25. Although the charging surface is notshown in the other alternative embodiments, one may be included and themagnet, shield, sleeve, may be aligned above or below the chargingsurface or flush with the charging surface. One side of the magnet maybe seated within the cavity 930 and the other side of the magnet 924,cavity 930, and the surface of the coil 914 may all be flush with eachother, as shown in FIG. 26. One side of the magnet and cavity 930 may beflush with each other but extend above the height of the surface of thecoil 914, as shown in FIG. 27. One side of the magnet 924 may be flushwith the shield while the shield is seated in the cavity 930, as shownin FIG. 28. The magnet 924 may be seated flush within a partiallyrecessed cavity 930, as shown in FIG. 29. The magnet 924 may be seatedflush within an inverted cavity 930 where the inverted cavity is flushwith the surface of the coil 914, as shown in FIG. 30. The magnet 924may be seated flush within an inverted cavity 930 where the invertedcavity extends above the surface of the coil 914, as shown in FIG. 31.The inverted cavity 930 may be recessed beneath the shield 962, as shownin FIG. 32. The inverted cavity 930 may be partially recessed, as shownin FIG. 33.

Although the charging surface 929 is only illustrated in a few of thefigures to make understanding the positional relationships between thevarious elements easier, it is to be understood that the chargingsurface may be included in these various embodiments in a variety ofdifferent locations and may have a variety of different characteristicsas discussed above with reference to the other embodiments.

The above description is that of the current embodiment of theinvention. Various alterations and changes can be made without departingfrom the spirit and broader aspects of the invention as defined in theappended claims, which are to be interpreted in accordance with theprinciples of patent law including the doctrine of equivalents. Anyreference to claim elements in the singular, for example, using thearticles “a,” “an,” “the” or “said,” is not to be construed as limitingthe element to the singular.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. A magnetic positioningsystem for use in an inductive power supply system for wirelesslytransferring power from an inductive power supply to a remote deviceusing an electromagnetic field, said magnetic positioning systemcomprising: a bonded magnet having a first polarity aligned with a firstmagnetic axis of said bonded magnet, wherein said first polarity andsaid first magnetic axis of said bonded magnet are substantiallyperpendicular to a power transfer surface; a second magnet having asecond polarity aligned with a second magnetic axis of said secondmagnet, said second polarity being opposite from said first polarity ofsaid bonded magnet, wherein said second polarity and said secondmagnetic axis of said second magnet are substantially perpendicular tosaid power transfer surface; wherein said bonded magnet and said secondmagnet are located in the electromagnetic field, wherein said bondedmagnet and said second magnet are located in at least one of saidinductive power supply and said remote device, wherein the other of saidinductive power supply and said remote device includes a magneticelement; wherein said bonded magnet is paired with the magnetic elementto cooperate with the magnetic element to provide magnetic attractionforce for alignment of said inductive power supply and said remotedevice; and wherein said second magnet is unpaired such that saidmagnetic positioning system is absent an attraction magnet thatcomplements said second magnet, wherein said second magnet provides amagnetic repulsion force in cooperation with the magnetic element foralignment of said inductive power supply and said remote device, whereinsaid magnetic attraction force and said magnetic repulsion forcecooperate to align said inductive power supply and said remote devicesuch that said first magnetic axis of said bonded magnet and a magneticaxis of said magnetic element are moved into coaxial alignment.
 2. Themagnetic positioning system of claim 1 further comprising an additionalmagnet located in at least one of said inductive power supply and saidremote device, said additional magnet location being different from saidbonded magnet location, wherein said second magnet is unpaired with saidadditional magnet such that said magnetic positioning system is absentattractive cooperation between said second magnet and said additionalmagnet.
 3. The magnetic positioning system of claim 1 further comprisinga ferrous element located in at least one of said inductive power supplyand said remote device, said ferrous element location being differentfrom said bonded magnet location.
 4. The magnetic positioning system ofclaim 1 wherein said bonded magnet includes at least one of bondedneodymium and bonded samarium cobalt.
 5. The magnetic positioning systemof claim 1 wherein said bonded magnet is bound together by a binder. 6.The magnetic positioning system of claim 5 wherein said binder iselectrically non-conductive.
 7. The magnetic positioning system of claim1 wherein said bonded magnet includes particles of a rare earth magnet.8. The magnetic positioning system of claim 7 wherein said rare earthmagnet is a ceramic ferrite magnet.
 9. A magnetic positioning system foruse in an inductive power supply system for wirelessly transferringpower from an inductive power supply to a remote device using anelectromagnetic field, said magnetic positioning system comprising: afirst magnet having a first polarity aligned with a first magnetic axisof said first magnet, wherein said first polarity and said firstmagnetic axis of said first magnet are substantially perpendicular to apower transfer surface; a second magnet having a second polarity alignedwith a second magnetic axis of said second magnet, said second polaritybeing opposite from said first polarity of said first magnet, whereinsaid second polarity and said second magnetic axis of said second magnetare substantially perpendicular to said power transfer surface; whereinsaid first magnet and said second magnet are located in at least one ofsaid inductive power supply and said remote device, wherein the other ofsaid inductive power supply and said remote device includes a magneticelement; wherein said first magnet is paired with the magnetic elementto cooperate with the magnetic element to provide a magnetic attractionforce for alignment of said inductive power supply and said remotedevice; wherein said second magnet is unpaired such that said magneticpositioning system is absent an attraction magnet that complements saidsecond magnet, wherein said second magnet provides a magnetic repulsionforce in cooperation with the magnetic element for alignment of saidinductive power supply and said remote device; wherein said magneticattraction force and said magnetic repulsion force cooperate to alignsaid inductive power supply and said remote device; and a shield toreduce the electromagnetic field that reaches at least one of said firstmagnet and said second magnet during wireless power transfer from saidinductive power supply to said remote device.
 10. The magneticpositioning system of claim 9 further comprising a third magnet locatedin proximity to said first magnet, wherein said third magnet providesadditional magnetic force for alignment of said inductive power supplyand said remote device.
 11. The magnetic positioning system of claim 10wherein said first magnet and said third magnet sandwich said shield.12. The magnetic positioning system of claim 9 wherein said shieldincludes a hole, wherein said first magnet is disposed within said holeof said shield.
 13. The magnetic positioning system of claim 9 whereinsaid shield includes a sleeve, wherein said first magnet is disposedwithin said sleeve of said shield.
 14. The magnetic positioning systemof claim 9 wherein said shield includes a cavity, wherein said firstmagnet is disposed within said cavity of said shield.
 15. The magneticpositioning system of claim 9 wherein said first magnet is flush with acharging surface of said inductive power supply.
 16. The magneticpositioning system of claim 9 wherein said shield is flush with acharging surface of said inductive power supply.
 17. The magneticpositioning system of claim 9 wherein said at least one of saidinductive power supply and said remote device is rotatable with respectto said first magnet and wherein at least one of said inductive powersupply and said remote device at least one of receives and transmitspower during said rotation.
 18. A magnetic positioning system for use inan inductive power supply system for wirelessly transferring power froman inductive power supply to a remote device using an electromagneticfield, said magnetic positioning system comprising: at least one of saidinductive power supply and said remote device including: a first magnethaving a first polarity aligned with a first magnetic axis of said firstmagnet, wherein said first polarity and said first magnetic axis of saidfirst magnet are substantially perpendicular to a power transfersurface; a second magnet having a second polarity aligned with a secondmagnetic axis of said second magnet, said second polarity being oppositefrom said first polarity of said first magnet, wherein said secondpolarity and said second magnetic axis of said second magnet aresubstantially perpendicular to said power transfer surface, wherein saidsecond magnet is unpaired such that said magnetic positioning system isabsent an attraction magnet aligned with said second magnet forattraction; the other one of said inductive power supply and said remotedevice including: a third magnet having a third polarity opposite fromsaid first polarity of said first magnet; wherein said first magnet andsaid third magnet are paired to provide a magnetic attraction force;wherein said second magnet and said third magnet provide a magneticrepulsion force; wherein said magnetic attraction force and saidmagnetic repulsion force cooperate to align said inductive power supplyand said remote device; and wherein at least one of said magnets is atleast one of bonded and shielded.
 19. The magnetic positioning system ofclaim 18 further comprising a fourth magnet that provides at least oneof an additional magnetic attraction force and an additional magneticrepulsion force for aligning said inductive power supply and said remotedevice, wherein said second magnet is unpaired with said fourth magnetsuch that said magnetic positionig system is absent attractivecooperation between said second magnet and said fourth magnet.
 20. Themagnetic positioning system of claim 18 wherein said magnetic attractionforce and said magnetic repulsion force provide tactile user feedback ona blind surface to allow a user to align said remote device and saidinductive power supply for charging.
 21. A magnetic positioning systemfor use in an inductive power supply system for wirelessly transferringpower from an inductive power supply to a remote device using anelectromagnetic field, said magnetic positioning system comprising: atleast one of said inductive power supply and said remote deviceincluding a first plurality of magnets, each of said first plurality ofmagnets having a first polarity aligned with a first magnetic axis,wherein said first polarity and said first magnetic axis aresubstantially perpendicular to a power transfer surface, wherein saidfirst magnetic axes of said first plurality of magnets are substantiallyaligned with each other; the other one of said inductive power supplyand said remote device including a second plurality of magnets and atleast one third magnet, each of said second plurality of magnets havinga second polarity aligned with a second magnetic axis, the at least onethird magnet being unpaired such that said magnetic positioning systemis absent an attraction magnet aligned with said at least one thirdmagnet for attraction, wherein said second polarity and said secondmagnetic axis are substantially perpendicular to said power transfersurface, wherein said second magnetic axes of said second plurality ofmagnets are substantially aligned with each other; wherein said secondpolarity of said second plurality of magnets is opposite said firstpolarity of said first plurality of magnets, wherein said at least onethird magnet has a third polarity similar to said first polarity;wherein said first plurality of magnets and said second plurality ofmagnets are paired to provide a magnetic attraction force for alignmentof said inductive power supply and said remote device into a pluralityof different positions, wherein at least one of said first plurality ofmagnets and said at least one third magnet provide a magnetic repulsionforce for alignment of said inductive power supply and said remotedevice; and wherein at least one of said magnets is at least one ofbonded and shielded.